During 2024 and 2025 and with support from Missouri Soybean Merchandising Council, we surveyed 200 soybean fields across 81 Missouri counties to better understand which plant-parasitic nematodes are present and their population densities. Fields were sampled across all nine Missouri crop reporting districts, giving us a statewide look at the nematodes associated with soybean production (Figure 1).

Figure 1 Distribution of 200 soybean fields sampled across 81 Missouri counties during the 2024-2025 statewide soybean nematode survey. Gold points indicate individual sampled fields. Missouri crop reporting districts are labeled by region and district code.

Nematodes are common across Missouri soybean fields

Ten types (or taxa) of plant-parasitic nematodes were detected. Spiral nematode (Helicotylenchus spp.), root-lesion nematode (Pratylenchus spp.), and soybean cyst nematode (SCN; Heterodera glycines) were the most common and present in 85%, 84%, and 80% of fields, respectively. Stunt (Tylenchorhynchus spp.) and lance (Hoplolaimus spp.) nematodes were detected less frequently, while root-knot (Meloidogyne spp.), dagger (Xiphinema spp.), pin (Paratylenchus spp.), ring (Criconematidae), and stubby-root (Trichodoridae) nematodes were more localized (Figure 2).

Figure 2 Prevalence (% of fields with detection) and population densities of plant-parasitic nematodes detected in 200 soybean fields across 81 counties in Missouri. Median and maximum population densities are based on positive soil samples only and are reported per 100 cm³ of soil. In the host column, icons indicate the potential to feed on soybean and/or corn. Host status may vary among nematode species within each group.

Multiple nematodes were common, with nearly half of the fields (47%) having three different plant-parasitic nematode taxa present. However, presence does not necessarily mean economic damage. Risk depends on the nematode, population density, crop, and field conditions.

SCN remains the nematode to watch

SCN stood out because it combined widespread presence and high egg counts. For fields that tested positive, the statewide median was approximately 2,100 eggs/100 cm³ soil (about 1/2 cup of soil). Populations varied considerably among fields and regions, with maximum counts reaching nearly 34,000 eggs/100 cm³.

We also tested how well these Missouri SCN populations reproduce on common sources of SCN resistance. SCN reproduction is measured using a Female Index (FI), which compares how many females develop on a resistant soybean versus a susceptible one. Lower values indicate less SCN reproduction and better resistance. Unfortunately, for every 100 SCN females developing on a susceptible soybean, the median Missouri population produced about 66 females on PI 88788 (the most common SCN resistance source found in Missouri soybean). All SCN populations tested were able to overcome PI 88788 resistance at varying levels.

The Peking type of SCN resistance performed better. Approximately half of the populations tested could reproduce well on Peking, but median reproduction was only about 10 females for every 100 on the susceptible soybean.

This pattern was also observed across regions. Regional FI scores ranged from 55 to 75 on PI 88788 compared to 3 to 17 on Peking.

What could this mean for yield?

Using the statewide median of 2,100 SCN eggs/100 cm³ soil and a Female Index of 66 on PI 88788, along with representative Missouri conditions of 12% sand, pH 6.5, 50 bu/acre expected yield, and a $13/bu soybean price, the SCN Coalition Profit Checker estimated a potential yield loss of 8.9%, or about 4.5 bu/acre and $58/acre. Actual estimates depend on SCN population density, virulence (ability to reproduce on the soybean), field conditions, expected yield, and soybean price.

What can growers do?

Management starts with knowing which nematodes are present and at what population levels. For SCN, use resistant varieties, rotate resistance sources such as PI 88788 and Peking, and rotate with a nonhost crop such as corn. Nematode-protectant seed treatments may also provide early-season protection as part of an integrated management program.

Management options for other nematodes depend on the species and population density. Several can reproduce on both soybean and corn, and resistant varieties are not available for many of them. Crop rotation, variety selection where resistance is available, and nematode-protectant seed treatments are potential options depending on the nematode and field history.

Don't guess. Sample. Missouri soybean growers can submit up to four soil samples for free SCN egg counts through SCN Diagnostics, supported by the Missouri Soybean Merchandising Council.

Missouri Nematode Reports by Region

Central
East Central
North Central
Northeast
Northwest
Southeast
Southwest
West Central